Msgut : the next Avtar

We report the viability of the Type I seesaw mechanism in 3 generation renormalizable SO(10) GUTs based on the 210 − 10 − 126 − 126− 120 Higgs system. The 120 -plet and 10-plet Higgs fit charged fermion masses while small 126-plet couplings enhance Type I seesaw neutrino masses to viable values and make the fit to light fermions accurate. For the 3 generation CP conserving case we display accurate charged fermion fits (χ tot < .2) which imply Type I neutrino masses 10 − 10 times larger than the 10 − 126 scenario. The correct ratio of neutrino mass squared splitting, large(θ 23 ) and small(θ 13 ) mixing angle are achievable. θ 12 is however small and indicates that -as in the Type I 10 − 126 case a fully realistic fit to the lepton mixing data also requires CP violation.